Plaster wall shrinkage and expansion control



Oct. 2, 1962 J. D. MCNULTY 3,056,233

PLASTER WALL SHRINKAGE AND EXPANSION CONTROL Filed July '7, 1958 2 Sheets-Sheet 2 IN VENTOR.l

JGBEPH D. MCNULTY M ATTYs United States Patent Oil 3.55233 Patented st. 2, 192

3,655,233 PLASTER WALL SHRiNKAGE AND EXPANSION CUNTFRL Joseph D. McNulty, 1366 N. Dearborn St., Chicago, Ill. Filed .filly 7, 1953, Ser. No. 74E-6,693 2 Claims. (Cl. Sil- 194) This invention relates to plaster Wall shrinkage and expansion control, and more particularly to the control of cracks or voids arising from the shrinkage or expansion of Portland cement plaster as applied to expansion joints.

By the term wall, I intend to include herein ceiling wa'lls and floor Walls as well as the usual side walls of a building or other structure, and the term wall is, therefore, used in this generic sense in the following description.

In the application of Portland cement plaster to building or structural walls equipped with the usual expansion joints about which the plaster is to be applied, it is found that in the shrinking of the plaster during setting, cracks form near or away from the expansion joints, and such cracks permit water, as from rain, snow, or sleet, to penetrate the crack spaces and freeze. The continued freezing and thawing enlarges the crack by causing spalling at the edges, and in time will destroy the wall. The cracks provide undesirable breeding areas for germs and for the collection of impurities, and further present an unsightly appearance. Even when caps or covers are applied to the joints, it is found that the irregular cracks formed extend beyond the caps and follow irregular patterns. lf it were possible to control the shrinking of the plaster so that the crack or void occurs at a precise location each time, the joints could then be effectively capped for concealing and enclosing the voids, etc., and a substantial advance in the plastering field would be achieved.

Problems further arise in connection with lath walls as well as masonry walls, and with the problem of shrinkage and expansion with respect to the studs and associated structure in such lath walls.

An object of the present invention is to provide a method and means for controlling crack formation and shrinkage and expansion in a plaster wall. A further object is to provide a method and means for controlling the crack formation or void formation during the shrinkage of the plaster wall so that the same could be completely enclosed by a joint cap having wings extending laterally of the joint. A still further object is to provide, in combination with a structural Wall equipped with a plaster expansion joint, a film of anti-bonding material about the expansion joint adapted to abut the plaster in the forming of the wall whereby during the shrinking of the wall, a controlled space will be obtained lying closely adjacent the expansion joint itself, and a cap covering the spacing, and the plaster being in effect a floating wall which may move outwardly from the joint or inwardly toward the joint while the joint remains stationary and a cap engaging the joint slidably engages the shrinking or expanding wall. With this structure the retainer is installed and the base coat and finish coat are worked to the retainer using the retainer or joint as a ground; the cover plate then covers the edge of the finish coat as well as the base coat because it is installed after the finish coat is in place. Other specific objects and advantages will appear as the specification proceeds.

The invention is shown, in an illustrative embodiment, by the accompanying drawing, in which- FIGURE l is a broken perspective View setting forth a structure embodying my invention; FIG. 2, a broken enlarged sectional view showing the plaster at the time of formation of the plaster wall; FIG. 3, a view similar to FIG. 2 but showing the structure after shrinkage of the Portland cement plaster; FIG. 4, a View similar to FIG. 2 but omitting the cap or cover; FIG. 5, a perspective View of a metal stud or lath wall with which. my invention is employed.

In the illustration given in FIGS. l to 4, inclusive, 10 designates a masonry wall which may consist of concrete block or any other suitable wall material. It will be Iunderstood that the present invention may be applied to any type of wall. To the wall lil is anchored by bolts 11, or other suitable means, an expansion joint 12, which may be of any desired shape or material. I prefer to employ a metal expansion joint having flanges 13 adapted to be secured to the wall 10 and having also a cup-shaped expansion end 14, as illustrated best in FIGS. 2 and 3. Such a joint, while the same is stationary and anchored upon the txed wall 10, is resilient and yields under pressure, accommodating itself to plaster movements.

As above stated, it is found that metal joints of this character, after becoming bonded to the Portland cement plaster, tenaciously hold a portion of the plaster thereon during the shrinking of the wall and cracks occur at some distance from the joint, thus making control or closing thereof a diflicult and uncertain operation. I have discovered that by applying an anti-bonding agent or film 15 to the outer surfaces of the expansion joint 12, as illustrated best in FIG. 2, the Portland cement plaster Wall 16 does not bond to the expansion joint and, instead, the plaster wall 16 moves independently of the permanent or anchored joint 12. As a result of the shrinkage of the plaster, it is found that an even or uniform void or crack 17 is formed on each side of the joint, as illustrated in lFIG. 3, and because the crack is located in adjacent relation to the joint, the crack can be readily controlled by the joint cap 18. The joint cap 18 preferably has an inner spring leg 19 adapted to releasably engage the cupshaped portion 14 of the expansion joint so as to effectively hold the cap in place, and the wing portions 20 of the cap which extend laterally of the portion 19 are effective in covering the voids or cracks 17 caused by the movement of the floating plaster wall 16 away from the joint 12. Any suitable means for anchoring the cap upon the retainer or joint may be employed.

The anti-bonding agent or film `1S may be any lubricant material such as grease, mineral oil, etc., or any substance which prevents the Portland cement 16 from forming a bond with the metal joint 12. It will be understood that a wide range of materials which will coat and protect the surfaces of joint 12 and which will prevent bonding of the cement to the joint 12, may be employed.

In the operation of the process illustrated in FIGS. 1-4, inclusive, the joint 12 is permanently anchored upon the wall 10 by any suitable means, the outer surfaces of the joint 12 which will engage the plaster then preferably coated with oil or any tanti-bonding material, and the v plaster wall then formed in situ in the usual manner.

As the plaster sets, shrinkage occurs and the plaster wall moves as a unit away from the coated walls of the joint so that the crevice or void formed lies always accurately adjacent the walls of the joint. The cap 18 is placed in position preferably after setting, and the wings 20 thereof are effective in forming a seal of the voids 17. As eX- pansion occurs when the wall becomes heated, such eX- pansion can occur within the spaces 17 without the forming of cracks and during expansion or contraction under temperature conditions, the cap 18 remaining as an effective seal about the spaces 17.

The cap 18 may be secured in position by the friction of the member 19 engaging joint end 14, or it may be sealed in position by the use of mastic (not shown) or other material. Preferably, any sealing compound is one which `'will permit ready yielding movement of the cap with respect to the yiioating plaster wall 16, and such a material may include not only mastic but lubricant or other material which provides an effective seal during sliding relative movement of the Portland cement Wall 16 with respect to the joint 12.

In the specific illustration, I have set out a type of expansion joint known as a flush joint. There are, of course, many types of expansion joints, including internal corner joints, external `corner joints, and the joints may be of widely varying shape. Further, the cap or cover 18 lmay have different shapes to fit corner areas and irregular surfaces found in building structures. Since such structures are well known, it is believed sufficient herein to employ a single ush type expansion joint as illustrative of the invention.

In the modification illustrated in FIG. 5, the invention is :shown applied to a plaster wall provided with metal wire studs, and means are provided to permit controlled expansion of the wall away from the wire studs `as well as away from the expansion joint. In the illustration given, a wire stud 21, which comprises a pair of spaced wires 22 between which is welded a zigzag wire 23, is provided for supporting a wall and for receiving plaster thereon. Anchored to the stud 21 is la tie-plate 24 secured to the stud by tie-wires 25. An expansion joint 26 is secured to the plate 24 by screws 27 or by any other suitable means, and the expansion joint is covered with a layer of oil 28 in the manner heretofore described in connection with FIGS. 1-4, inclusive. While, in FIG. 5, the expansion joint 26 is :shown extending in a direction parallel to the stud 21, it may be extended in a direction transverse to the vertically extending stud member 21.

To insure that the plaster will not stick to the stud 21, and enabling it to shrink readily away therefrom, I provide paper strips or webs 29 on each side of the stud 21, and the paper also is preferably provided with a grease coat or oil coat, etc. to cause the concrete wall to shrink away from the stud.

Where, as indicated above, the expansion joint and stud are in vertical alignment and the greased paper 29 and oil layer 28 are employed, it will be found that the plaster wall as a single unitary structure may shrink away from the joint and stud `simultaneously to provide a uniform spacing between the Wall and the stationary stud and stationary joint. Irrespective of the location of the expansion joint with respect to the stud, shrinkage of the wall can occur in different directions by reason of the location of the oil layer and the paper layers as described.

A pressed steel :stud may be substituted for the wire type stud shown in FIG. 5. It will -be understood that various types of metal studs may be employed and the studs may be enclosed within concrete walls 31, as illustrated in FIG 5.

While, in the foregoing specicat-ion, I have set forth a specific structure in considerable detail for the purpose of illustrating one imode in which the invention may be practiced, it will be understood that such details of structure or procedure may be varied widely by those skilled in the art Without departing from the spirit of my invention.

I claim:

l. In a wall structure, a metal stud, an expansion joint ymember secured to said stud, said expansion joint member having anti-bonding material coating the outer joint surfaces, a web enclosing said stud, Portland cement plaster forming a wall enclosing said stud and joint and prevented from bonding thereto by said anti-bonding -material and web, whereby said wall, being unbonded to said members, may move toward and away from said members under shrinking and expansion conditions, and cap means carried by said joint member and providing wings extending over said wall end portion to cover portions of the same during said shrinking and expansion movements.

2. The structure of claim l, in which said web is coated with grease.

References Cited in the file of this patent UNITED STATES PATENTS 997,214 Steiner July 4, 1911 1,163,198 Atterbury Dec. 7, 1915 1,444,709 Sea Feb. 6, 1923 1,988,029 vVOlfe Ian. 15, 1935 2,080,124 Friberg May 1l, 1937 2,125,136 Trojanowski July 26, 1938 2,540,251 Fischer Feb. 6, 1951 2,856,766 Huntley Oct. 21, 1958 

